The present invention relates, generally, to methods and means for measuring the cardiac output of a mammalian patient, more especially to noninvasive methods and means for measuring the cardiac output of a human patient, and most particularly to a dual modality insonification technique for ascertaining the cross-sectional area of the patient's ascending aorta and the systolic velocity profile of blood flow therethrough allowing for a determination of cardiac output, cardiac index, stroke volume and stroke index, amongst other physiological parameters.